Integrated process for producing ammonium nitrate

Abstract

A process for producing ammonium nitrate is disclosed and in which: a) a gaseous oxidizer feed composed at least substantially of ammonia, steam and an oxidizing gas is exposed to conditions whereby the ammonia is oxidized to produce a reaction mixture including nitrogen monoxide and water vapor, b) the reaction mixture is cooled in a heat exchanger whereby the nitrogen monoxide is oxidized, the water vapor is condensed and the products of the nitrogen monoxide oxidation react with and are absorbed by the condensed water to form a nitric acid stream, with substantially all of the nitrogen monoxide in the reaction mixture being converted to nitric acid, and c) the nitric acid stream is reacted with a stream of ammonia in an ammonium nitrate producing stage to form the ammonium nitrate. Substantially all of the steam within the oxidizer feed is derived from the ammonium nitrate producing stage, and at least 10% of the ammonia within the oxidizer feed is derived and carried by the steam from the ammonium nitrate producing stage. Also disclosed is ammonium nitrate, in any of its various possible forms, when produced by the disclosed process.

What is claimed is: 
     
       1. A process for producing ammonium nitrate in which:
 a) a gaseous oxidiser feed comprising ammonia, steam and an oxidising gas is exposed to conditions whereby the ammonia is oxidised to produce a reaction mixture including nitrogen monoxide and water vapour, 
 b) the reaction mixture is cooled in a heat exchanger whereby the nitrogen monoxide is oxidised, the water vapour is condensed and the products of the nitrogen monoxide oxidation react with and are absorbed by the condensed water to form a nitric acid stream, with substantially all of the nitrogen monoxide in the reaction mixture being converted to nitric acid, 
 c) the nitric acid stream is reacted with a stream of ammonia in an ammonium nitrate producing stage to form an ammonium nitrate solution, 
 d) at least 80% of the steam within the oxidiser feed is derived from the ammonium nitrate producing stage, and 
 e) at least 10% of the ammonia within the oxidiser feed is carried by the steam from the ammonium nitrate producing stage and is derived from ammonia that is excess to that stage. 
 
     
     
       2. A process as claimed in  claim 1  wherein the steam derived from the ammonium nitrate producing stage comprises about 100% of the steam component of the gaseous oxidiser feed. 
     
     
       3. A process as claimed in claim h wherein the ammonia derived from the ammonium nitrate producing stage comprises at least 80% of the ammonia component of the gaseous oxidiser feed, with the balance of the required ammonia feed being derived from a different source. 
     
     
       4. A process as claimed in  claim 1 , wherein the ammonia derived from the ammonium nitrate producing stage comprises about 100% of the ammonia component of the gaseous oxidiser feed. 
     
     
       5. A process as claimed in  claim 1 , wherein the steam and ammonia derived from the ammonium nitrate producing stage comprise about 100% of the steam and ammonia components respectively of the gaseous oxidiser feed. 
     
     
       6. A process as claimed in  claim 1 , wherein an ammonia feed is fed to the ammonium nitrate producing stage in an amount approximately equal to the total amount to be consumed in the ammonium nitrate producing stage and the nitric acid producing stage. 
     
     
       7. A process as claimed in  claim 1 , wherein the oxidising gas comprises a gas containing at least 80% oxygen. 
     
     
       8. A process as claimed in  claim 1 , wherein the oxidising gas comprises a gas containing at least 90% oxygen. 
     
     
       9. A process as claimed in  claim 1 , wherein the oxidising gas comprises a gas containing at least 95% oxygen. 
     
     
       10. A process as claimed in  claim 7 , wherein the oxidising gas in the oxidiser feed is provided in an amount sufficient to oxidise the ammonia in the oxidiser feed and substantially all of the nitrogen monoxide in the reaction mixture. 
     
     
       11. A process as claimed in  claim 7 , wherein the oxidising gas in the oxidiser feed is provided in an amount sufficient to oxidise the ammonia in the oxidiser feed and some of the nitrogen monoxide in the reaction mixture and wherein additional oxidising gas is added to the reaction mixture to facilitate substantially complete oxidation of the nitrogen monoxide in the reaction mixture. 
     
     
       12. A process as claimed in  claim 1 , wherein the oxidising gas comprises air. 
     
     
       13. A process as claimed in  claim 12  wherein the oxidising gas in the oxidiser feed is provided in an amount just sufficient to oxidise the ammonia in the oxidiser feed and wherein additional oxidising gas is added to the reaction mixture to facilitate substantially complete oxidation of the nitrogen monoxide in the reaction mixture, the additional oxidising gas being admitted to the reaction mixture following oxidising of the ammonia and prior to the heat exchanger. 
     
     
       14. A process as claimed in  claim 12 , wherein the oxidising gas is heated prior to mixing with the steam and ammonia components of the oxidiser feed. 
     
     
       15. A process as claimed in  claim 14  wherein the oxidising gas is heated by heat exchange with the reaction mixture. 
     
     
       16. A process as claimed in  claim 1 , wherein the ammonium nitrate solution is concentrated in an evaporator within the ammonium nitrate producing stage. 
     
     
       17. A process as claimed in  claim 16  wherein a phase separator is provided for receiving a two-phase (ammonium nitrate-steam) stream from the evaporator, and wherein steam is separated from the two-phase stream in the separator and is returned to the nitric acid producing stage, to form the steam component of the oxidiser feed, together with entrained ammonia that is supplied to the ammonium nitrate producing stage in excess of that consumed in reacting with the nitric acid. 
     
     
       18. A process as claimed in  claim 1 , wherein the ammonium nitrate solution is concentrated in two, first and second, series connected evaporators, wherein a first phase separator is provided for receiving a two-phase (ammonium nitrate-steam) stream from the first evaporator, and wherein steam is separated from the two-phase stream in the first separator and is returned to the nitric acid producing stage, to form the steam component of the oxidiser feed, together with entrained ammonia that is supplied to the ammonium nitrate producing stage in excess of that consumed in reacting with the nitric acid. 
     
     
       19. A process as claimed in  claim 18  wherein a second phase separator is provided for receiving a two-phase stream from the second evaporator, and wherein steam is separated from the two-phase stream in the second phase separator and is employed in a condensed state as wash water a demister device that is located in either one or each of the first and second phase separators. 
     
     
       20. A process as claimed in  claim 1 , wherein the nitrogen monoxide in an amount approaching 100% of that in the reaction mixture is converted to nitric acid in the nitric acid producing stage.